A significant advance in metal oxide semiconductor (MOS) technology was the introduction of polycrystalline silicon resistors which are formed in a dielectric layer overlying the silicon substrate. A polycrystalline silicon resistor comprises a strip of polycrystalline silicon formed in the dielectric layer overlying the substrate, the resistivity of the polycrystalline resistor being determined by the concentration of implanted doping impurities. By using ion implantation, the resistivity may be selected with great accuracy, a significant advantage. Furthermore, the polycrystalline resistor does not take up room on the underlying substrate, which improves device density on the integrated circuit.
One problem with polycrystalline silicon resistors is that transmission of a signal through a polycrystalline silicon resistor introduces noise into that signal which is inversely proportional to the frequency. This type of noise is commonly called flicker noise on 1/f noise. It is believed that this noise arises from the presence of surface states at the interface between the polycrystalline silicon resistor and the surrounding dielectric layer. The phenomenon of surface state noise is well known in the art. Polycrystalline silicon germanium has been studied by Chen, "Electrical and Noise Properties of Vacuum Deposited Thin Germanium Films", PhD Thesis, University of South Florida, 1976. Such noise is a significant problem if the polycrystalline semiconductor resistor is to be used as a photodetector load resistor in a charge coupled device imager array, because such noise degrades the quality of the image produced by the imager. Such noise is also a significant problem if the polycrystalline semiconductor resistor is to be used in a semiconductor memory such as a random access memory formed on an integrated circuit substrate, inasmuch as the 1/f noise can introduce errors into the memory. Accordingly, it has been a goal in the art to somehow eliminate or at least reduce 1/f noise in polycrystalline semiconductor resistors.